Need help with touring Hawaii

Have you taken a look at Road Scholar? They have some intergenerational programs for grandparents and grandkids. I did a quick search on the Road Scholar site using the filter for grand parents and 12 years old. Looks like there are a few in Hawaii if the itinerary is of interest to you.

https://www.roadscholar.org/find-an-adventure?intergen=true&page=1&pagesize=all&intergenminage=12

I too would recommend the Road Scholar inter-generational trips. We have not used them yet, but friends who have talked their grandchildren on several of their trips have nothing but good to say about it.

When you say "Hawaii" are you interested in touring the whole state of Hawaii or just the Big Island Hawaii? You may want to pick just 2 or 3 of the Islands with 4 or 5 days each - Oahu and Hawaii (Big Island) or Oahu and Maui. Or do three islands, 3 days each. Oahu is the developed island (i.e. Waikiki), Maui use to be the old Hawaii until discovered by tourist including Canadians, and the Big Island is both big and a geologic (volcano) wonder.

If you want to do self-guided look at the HawaiiRevealed guide books: https://www.hawaiirevealed.com/

And if you just show up at one or more of the islands, there will be a lot of tourist kiosks willing to sign up up with day tour packages and activities (snorkeling, whale watching etc).

If you want an escorted 'all done for you' type tour you may want to check this out

https://www.perillotours.com/hawaii/escorted-tours

Thank you to all who responded to my request.
So impressed with the roadscholar site. Now to get my granddaughter to make up her mind!
I will be using the forum in the future: especially in another 3 years when it is time for my grandson's trip. He has his eye on safari in Africa.
Again, my sincere thanks to all.

Used hawaiirevealed to create our own self guided trip 2 years ago. Toured Oahu and Maui with total of 6 people. Kids aged 13 to 21. It was truly paradise. The kids really enjoyed snorkeling, ziplining and a kayaking whale-watch trip. The adults were impressed by Pearl Harbor and a bike ride down Haleakala volcano plus a drive on the Hana highway! Try all the seafood--poke & sushi are amazing! Happy travels.

Many Americans do Hawaii DIY, no spendy 3rd party tours needed.
A good resource for my Hawaii visits has been to buy the "Ultimate Guidebook" book for whatever island(s) you're going to.
3rd party tours are more helpful in Europe, but IMO not so important for Hawaii.

Something you may also want to consider is a cruise around Hawaii, e.g. https://www.ncl.com/vacations?destinations=Hawaii_Cruises

Living in Hawaii most of the year, I know how expensive it is. If you are considering a totally organized tour of one or all of the islands, you will need LOTS of money. In my 32 years there I have never encountered a tour group there so good luck in finding something.
As someone else has posted, Hawaii (the state) is actually several islands. Most folks, unfortunately, only go to Oahu and stay in Waikiki which we call our Disneyland. The guide book series "(name of island) Revealed" is the best one by far. aloha charlie

Don't limit your trip to the island of Oahu.
Kauai is more natural and less developed, with spectacular hikes as well as resort beaches, you get both.
Big Island is you want live volcanoes, it's big compared to other islands, need a car.
Maui is less congested than Oahu, but has some of the same problems of over-development.
Lanai is for people who want to spend serious time golfing.
Molokai is the least developed, you can take a tour (escorted only) to the former Leper Colony, recommend the mule ride down the two thousand foot cliff but you can also fly into the Molokai airport. But don't go to Molokai if you're looking for night life.

The company Backroads has family trips to various Hawaii islands. They are more of an active/multi-sport company, so that may not be what you’re seeking but take a look at one example: https://www.backroads.com/trips/MLMIF/maui-lanai-biking-hiking-family-tour

If you’re new to the RS forum, there is a “Beyond Europe” category (under the country listings) where folks post questions related to U.S. travel. You may find some suggestions there in older threads.

I'm a little late jumping in here.....

You do not need a guided tour in Hawaii. Very easy to set everything up yourself, and lots of great guide books and internet forums to help out. You don't have to worry about speaking the language, or currency exchange, or driving on the wrong side of the road. Kent did a pretty good brief summary of the different islands (note the trail down the mountain to the leper colony is currently closed).

I suggest that you go to a maximum of two islands. Perhaps Oahu and the Big Island for the contrasts. Oahu has Pearl Harbor, the Polynesian Cultural Center, and watching the big wave surfing on the north shore. You could sign up for a day circle tour of the island, but you could also do a lot on your own. The Big Island has Hawaii Volcanoes National Park, plus some great white, black, and green sand beaches. It is a lot more authentic and easier to find more of the "old Hawaii". Driving around the island is really easy; there's one highway that goes all the way around.

In the early days of statehood, travel agents offered one week air-hotel-car packages, but even so, I believe that they were not full service guide supported tours. The big advertiser of these packages was Pleasant Hawaiian Holidays: https://www.pleasantholidays.com/Vacation-Deals-Hawaii

Once arrived with feet on ground, guided bus tours were more of the one day variety and the big provider was Roberts of Hawaii: https://www.robertshawaii.com/

And as said, the above English speaking tours not fully supported guided tours with a main guide augmented by local guides. I believe that the exception was/is the tour groups with limited English speaking skills. Even the Japanese are becoming more self-sufficient travelers with many Hawaii tourist oriented businesses staffed with multi-lingual service agents. The fully supported tour exception are biking/adventure tours with specialized vehicle support.

Given that you are from Toronto and participating in an English language forum, you should be able to cope with the local dialect and should have no problem with signage. The possible exception is street names. (Streets named since 1978 are required by law to have Hawaiian names). If you are English literate you should have no problem touring Hawaii. Many Canadians enjoy the Hawaiian winter season.

Your granddaughter may enjoy the Hilton at Waikiki, add a circle tour of the island. For beach time we loved Maui. Limit yourself to 2 island and enjoy the planning. We had friends that did a Hawaiian cruise and enjoyed that. Lucky granddaughters to have a grandma that loves to travel with her girls.